Question

我一直在寻找一种放大和缩小图像视图的方法，但是问题在于，当任何人扯下它并且它可以从屏幕上消失时图像正在移动，我希望图像在静止时用户放大或缩小。

我试过这段代码：

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;

public class ZoomInZoomOut extends Activity implements OnTouchListener 
{
private static final String TAG = "Touch";
@SuppressWarnings("unused")
private static final float MIN_ZOOM = 1f,MAX_ZOOM = 1f;

// These matrices will be used to scale points of the image
Matrix matrix = new Matrix();
Matrix savedMatrix = new Matrix();

// The 3 states (events) which the user is trying to perform
static final int NONE = 0;
static final int DRAG = 1;
static final int ZOOM = 2;
int mode = NONE;

// these PointF objects are used to record the point(s) the user is touching
PointF start = new PointF();
PointF mid = new PointF();
float oldDist = 1f;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    ImageView view = (ImageView) findViewById(R.id.imageView);
    view.setOnTouchListener(this);
}

@Override
public boolean onTouch(View v, MotionEvent event) 
{
    ImageView view = (ImageView) v;
    view.setScaleType(ImageView.ScaleType.MATRIX);
    float scale;

    dumpEvent(event);
    // Handle touch events here...

    switch (event.getAction() & MotionEvent.ACTION_MASK) 
    {
        case MotionEvent.ACTION_DOWN:   // first finger down only
                                            savedMatrix.set(matrix);
                                            start.set(event.getX(), event.getY());
                                            Log.d(TAG, "mode=DRAG"); // write to LogCat
                                            mode = DRAG;
                                            break;

        case MotionEvent.ACTION_UP: // first finger lifted

        case MotionEvent.ACTION_POINTER_UP: // second finger lifted

                                            mode = NONE;
                                            Log.d(TAG, "mode=NONE");
                                            break;

        case MotionEvent.ACTION_POINTER_DOWN: // first and second finger down

                                            oldDist = spacing(event);
                                            Log.d(TAG, "oldDist=" + oldDist);
                                            if (oldDist > 5f) {
                                                savedMatrix.set(matrix);
                                                midPoint(mid, event);
                                                mode = ZOOM;
                                                Log.d(TAG, "mode=ZOOM");
                                            }
                                            break;

        case MotionEvent.ACTION_MOVE:

                                            if (mode == DRAG) 
                                            { 
                                                matrix.set(savedMatrix);
                                                matrix.postTranslate(event.getX() - start.x, event.getY() - start.y); // create the transformation in the matrix  of points
                                            } 
                                            else if (mode == ZOOM) 
                                            { 
                                                // pinch zooming
                                                float newDist = spacing(event);
                                                Log.d(TAG, "newDist=" + newDist);
                                                if (newDist > 5f) 
                                                {
                                                    matrix.set(savedMatrix);
                                                    scale = newDist / oldDist; // setting the scaling of the
                                                                                // matrix...if scale > 1 means
                                                                                // zoom in...if scale < 1 means
                                                                                // zoom out
                                                    matrix.postScale(scale, scale, mid.x, mid.y);
                                                }
                                            }
                                            break;
    }

    view.setImageMatrix(matrix); // display the transformation on screen

    return true; // indicate event was handled
}

/*
 * --------------------------------------------------------------------------
 * Method: spacing Parameters: MotionEvent Returns: float Description:
 * checks the spacing between the two fingers on touch
 * ----------------------------------------------------
 */

private float spacing(MotionEvent event) 
{
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
}

/*
 * --------------------------------------------------------------------------
 * Method: midPoint Parameters: PointF object, MotionEvent Returns: void
 * Description: calculates the midpoint between the two fingers
 * ------------------------------------------------------------
 */

private void midPoint(PointF point, MotionEvent event) 
{
    float x = event.getX(0) + event.getX(1);
    float y = event.getY(0) + event.getY(1);
    point.set(x / 2, y / 2);
}

/** Show an event in the LogCat view, for debugging */
private void dumpEvent(MotionEvent event) 
{
    String names[] = { "DOWN", "UP", "MOVE", "CANCEL", "OUTSIDE","POINTER_DOWN", "POINTER_UP", "7?", "8?", "9?" };
    StringBuilder sb = new StringBuilder();
    int action = event.getAction();
    int actionCode = action & MotionEvent.ACTION_MASK;
    sb.append("event ACTION_").append(names[actionCode]);

    if (actionCode == MotionEvent.ACTION_POINTER_DOWN || actionCode == MotionEvent.ACTION_POINTER_UP) 
    {
        sb.append("(pid ").append(action >> MotionEvent.ACTION_POINTER_ID_SHIFT);
        sb.append(")");
    }

    sb.append("[");
    for (int i = 0; i < event.getPointerCount(); i++) 
    {
        sb.append("#").append(i);
        sb.append("(pid ").append(event.getPointerId(i));
        sb.append(")=").append((int) event.getX(i));
        sb.append(",").append((int) event.getY(i));
        if (i + 1 < event.getPointerCount())
            sb.append(";");
    }

    sb.append("]");
    Log.d("Touch Events ---------", sb.toString());
}
}

Answer 1

您可能希望使用ScaleGestureRecognizer，而不是尝试手动解密触摸事件。当用户试图缩放时，它会干净地分离滚动（当用户打算平移时），然后忽略移动。

请参阅http://developer.android.com/training/gestures/scale.html#scale

在这种情况下，它会在绘制过程中缩放画布，但这应该相对容易地转换为setImageMatrix。

放大和缩小图像视图而不移动它

1 个答案: